Multicolour chromaticity sensor

Abstract

The present invention provides an optical sensor having one or more filter-photodetector pairs and feedback to monitor the intensity and chromaticity of the white light generated by an illumination system. According to the present invention, filter-photodetectors are configured into pairs thereof, wherein a first filter-photodetector of a pair is configured and arranged so as to be sensitive to a predetermined region of the electromagnetic spectrum, while a second filter-photodetector of the pair is configured and arranged to be sensitive to a substantially complementary region of the electromagnetic spectrum. The spectral responsivity of the first filter-photodetector and the second filter-photodetector overlap in a predetermined region of the electromagnetic spectrum. Furthermore, the spectral responsivity of the first filter-photodetector is configured to substantially monotonically increase with respect to wavelength within said predetermined region, while the spectral responsivity of the second filter-photodetector is configured to substantially monotonically decrease with respect to wavelength within said predetermined region.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Patent Application No. 60 / 683,436, filed May 20, 2005, which is incorporated herein, in its entirety, by reference.FIELD OF THE INVENTION[0002]The present invention relates to optical sensing devices, and more particularly to multicolour chromaticity sensing devices for use with lighting devices.BACKGROUND OF THE INVENTION[0003]Light-emitting diodes (LEDs) are semiconductor devices that convert electrical energy directly into visible light of various colours. With the advent of high-flux LEDs, luminaires are progressively being moved from the traditional incandescent or fluorescent lamps to LEDs for increased reliability, higher luminous efficacy and lower maintenance costs. LED-based luminaires are increasingly becoming the architecture of choice in a variety of mainstream commercial applications such as accent lights, wall washing, signage, advertising, decorative and display lighti...

AI Technical Summary

Problems solved by technology

While it can be difficult and expensive to manufacture suitable filter-photodetector combinations to approximate the colour matching functions of the human visual system, tristimulus colour sensors may be used to directly measure white light intensity and chromaticity.

In practice, however, the spectral responsivities of commercial tristimulus colour sensors such as those manufactured by Hamamatsu™ and TAOS™ can only roughly approximate the CIE colour matching functions.

Third, even if the spectral power distributions of the colour LEDs and the spectral responsivities of the filter-photodetector combinations of the tristimulus colour sensor do not overlap, any change in the dominant wavelengths of the light produced by the LEDs can result in changes in the tristimulus sensor output.

If the LEDs' spectral power distributions themselves overlap, for example as occurs with red and amber LEDs, optical crosstalk will be unavoidable with tristimulus colour sensors.

However, most spectroradiometer designs require precision optics and a considerable volume of space that is incompatible with microelectronic subsystems.

Moreover, most of the existing spectroradiometer designs are typically difficult to fabricate, especially those based on micromachined moving parts.

The spectroradiometer approach fails in that such devices are generally complex and expensive to manufacture, and they generate an overabundance of data that must be analyzed to obtain a few significant values, for example LED intensity and dominant wavelength.

A disadvantage of the photodiode design disclosed by Carr is that it can be difficult to obtain predetermined and desirable spectral responsivities solely through the use of semiconductor manufacturing techniques.

As a result, the spectral resolution of Carr's photodiodes may be poor, particularly in the presence of electrical noise.

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